The present invention relates to corneal onlay lenses and to methods for attaching such lenses to the cornea. More particularly, the invention relates to lenses and to lens attachment methods in which the lens has increased resistance to being removed.
Currently, epikeratophikia lenses are attached to the cornea by tucking the tapered lens edge into a circular groove cut into the peripheral cornea. A suture is then passed through the lens and cornea to attach the lens. With time, scarring occurs in this peripheral groove which functions to permanently fixate the lens to the cornea. The suture can then be removed.
This approach to permanently fixating epikeratophikia lenses has various limitations or problems, in particular, if the lens is made of certain synthetic materials. For example, the desired scarring may not occur. Also, suturing may not be practical because of the mechanical strength of the lens material or for other reasons. Thus, it would be advantageous to have lens designs and methods of lens attachment which do not present such difficulties.
Peyman et al U.S. Pat. No. 4,646,720 discloses a corneal onlay lens including at least one opening for the diffusion of nutrients from the recipient's cornea. These openings, which can be located anywhere through the lens, do not play any direct role in attaching the lens to the cornea and must remain open in order to provide for the flow of nutrients.
Abel, Jr., U.S. Pat. No. 4,693,715 discloses a corneal implant which includes a series of through bores for receiving sutures to couple the implant to the cornea. These through bores extend from the top or anterior surface of the lens to the periphery of the lens. In place, the periphery of the lens abuts the cornea, but is not covered by any corneal tissue.
H. Cardona, in an article entitled "Prosthokeratoplasty", Cornea 2:pp 179-183, 1983, describes a keratoprosthesis including an optical cylinder made of methyl methacrylate with a contact lens glued to its anterior surface, and a TEFLON ring with multiple small and large openings. This TEFLON skirt is sutured over the anterior surface of the cornea. The openings in the TEFLON ring are there to allow recipient corneal tissue to grow through. This system is quite cumbersome and, since the TEFLON (polytetrafluoroethylene) ring is entirely over the corneal, tends to be easily moved out of position. A lens and attachment method with which provides for more secure lens attachment is clearly needed.